This invention relates to rollers in general and more particularly to an improved roller of the type having a corrosion-free outer sleeve mounted to a cylindrical core.
Grooved rollers some of which may have a quite large working width are often used in processes such as those found in the paper industry where such rollers are used to remove moisture from paper, cardboard or the like. Because they come in contact with moisture, at least the outer surface of the roller must be made of a metal or alloy which will not corrode, suitable materials being stainless steel, chilled iron or the like. Because of the initial cost of the metal and because such metals are generally not easily workable, such rollers are quite expensive to manufacture. In order to reduce these costs, roller have been developed which comprise an inner cylindrical core of a conventional metal with a relatively thin outer sleeve or cladding of the corrosion resistant metal. Generally, the outer sleeve is manufactured in a single piece using a mold and a centrifugal casting process. This requires that a separate mold be provided for each different size roller. Even though rolls of the same diameter are being manufactured, each one of different length requires a separate mold.
Typically the sleeve is heated and then slipped over the central core and secured in place through heat shrinking. Because the rollers very often have an extremely long length, this heat shrinking process becomes quite difficult. The sleeve cannot be heated to too high a temperature because of the risk of uneven stresses and distortion and thus, at the level to which it is normally heated the remaining tolerance between the inner surface of the sleeve and the outer surface of the core is quite small. The result is that unless extreme care is taken while the sleeve is being placed on the core, premature contact of the sleeve and the core can occur resulting in a shrinking and hardening of the sleeve and core before the sleeve has been completely moved in place. Attempts have been made to overcome this problem by slightly tapering the sleeve and core so that a large clearance is present as the sleeve is first slipped over the core which clearance gradually decreases as they come to their final relative positions.
Because of the hardness of the outer sleeve, it is difficult to cut the necessary grooves therein and such a procedure may require considerable time. For example, times in excess of a month may be required to manufacture a sleeve for a very large roller. In addition, the manufacturing process requires the use of a very large machine.